The concentration of pollen in the air could affect the rate of SARS-CoV-2 infection, according to a recent study by an international team of researchers.
In 2020, the early spring coronavirus outbreak in China became known worldwide. Did environmental factors such as temperature or humidity contribute to its thriving? A study published in PNAS, conducted by German, Spanish and American scientists, offers some answers to this question. According to the study, temperature, humidity, and most importantly, pollen concentration in the air positively influence the rate of SARS-CoV-2 infection.
In fact, pollen is known for its immunosuppressive effect on the respiratory tract. It inhibits the production of interferons, an essential component of antiviral immunity, thus facilitating infection by seasonal respiratory viruses. This hypothesis, which has not yet been tested for SARS-CoV-2, appears to explain the observations of the international research team.
Pollen appears to influence coronavirus infection rates
The researchers collected climate and pollen quantity data from 31 countries, mainly in Europe, from March to April 2020, during which time the average pollen quantity was 240 pollen grains per cubic meter of air. The scientists examined the rate of coronavirus infection while the epidemic was in its exponential phase as a function of four variables: low and high pollen amounts in the air, low and high population density. They found that pollen increased the infection rate in sparsely populated areas, and even more so in densely populated areas. Thus, densely populated areas with a high concentration of pollen in the air had the highest infection rate.
The researchers note in their paper that pollen is a modulating factor in the progression of SARS-CoV-2 infections and can increase infection rates by 10-30%. For example, without containment, an increase in pollen concentration of 100 grains per cubic meter of air increases the coronavirus infection rate by 4%. This positive correlation between infection rate and pollen amount was observed in all countries studied but was statistically significant for only six of them, including.
Pollen a catalyst for infection
Coronavirus is transmitted by close human-to-human contact, so containment measures have significantly reduced infection rates, making the effect of pollen on virus infection rates much smaller. Without contact, the infection does not occur and the pollen itself does not carry the virus. It acts as a catalyst for infection by lowering the immune response. These results are independent of the allergenic nature of the pollen and apply to the general population, although the researchers did not have access to the allergy history of the Covid 19 patients. The effect observed here is likely to be exacerbated in individuals who are already allergic to pollen or who are asthmatics.
As spring is already upon us and the concentration of pollen in the air is bound to rise it is more important now to wear masks especially for subjects that are asthmatic or have allergies.